Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2000-02-02
2001-11-06
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06313550
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electric motors that are particularly useful with a lithographic device for the fabrication of integrated circuits on semiconductor wafers. More specifically, the present invention relates to a system for mounting and cooling a plurality of spaced apart coils for linear or planar electric motors.
BACKGROUND
Linear and planar electric motors are used in a variety of devices and systems. For example, linear and planar electric motors are used to precisely position a semiconductor wafer during photolithography and other semiconductor processing. The accurate positioning of the wafer during processing is critical to creating high density semiconductor wafers. Alternately, linear or planar motors are used in other devices, including elevators, electric razors, machine tools, metal cutting machines, inspection machines and disk drives.
A linear electric motor generally has a one-dimensional magnet assembly and a one-dimensional coil assembly positioned along the magnet assembly. A planar electric motor generally has a two-dimensional magnet assembly and a two-dimensional coil assembly positioned near the magnet assembly. Electric current in the coil assembly creates a force between the coil assembly and the magnet assembly that can be used to move one of the assemblies relative to the other assembly.
The coil assembly for a linear or planar motor typically includes a coil base having a generally planar, upper surface and a plurality of spaced apart, coils directly secured to the upper surface of the coil base with an adhesive. Mounting the coils directly to the coil base provides a good mechanical connection between the coils and the coil base. This enhances motor controllability and reduces vibration.
Unfortunately, existing linear or planar electric motors are not entirely satisfactory. In particular, electrical current in the coils produces heat due to resistance in the coils. The coils have limited thermal conductivity. During operation, the coils are at a higher temperature than the surrounding environment. Thus, during operation, heat from the coils is transferred to the surrounding environment, including the air surrounding the electric motor and the other components positioned near the electric motor. The heat changes the index of refraction of the surrounding air. This reduces the accuracy of an interferometer system used to monitor the position of the motor and degrades machine positioning accuracy.
As a result thereof, in some applications, including photolithography, it is necessary to accurately control the temperature of the external surfaces of the motor. With the coils glued directly to the coil base, heat from the coils is transferred directly to the upper surface of the coil base and the parts attached to the coil base. Thus, cooling must be provided to both the coil and the side of the coil base that is opposite the coils in order to control the temperature of the external surfaces of the motor.
Additionally, the direct attachment of the coils to the upper surface of the coil base can create a thermal distortion of the coil assembly. In particular, the coils typically are made of a material having a higher coefficient of thermal expansion than the coil base. Further, during operation, the coils are at a higher temperature than the coil base. As a result thereof, the coils expand relative to the coil base. The differential in expansion creates thermal stress in the coils and the coil base and can cause the coil assembly to bend and flex. This reduces the accuracy of movement of the motor.
In light of the above, it is an object of the present invention to provide a device and method for mounting coils in an electric motor that provides a rigid mechanical connection between the coils and the rest of the motor and good thermal isolation of the coils from the rest of the motor. Yet another object of the present invention is to provide a device and method for mounting coils in an electric motor that allows the coils to expand and minimizes thermal distortion. It is another object of the present invention to provide a cooling system to maintain the external surfaces of the motor at a set temperature.
SUMMARY
The present invention is directed to a coil assembly for a linear or planar motor that satisfies these needs. The coil assembly includes a plurality of coils and a coil base having a plurality of coil supports for securing the coils to the coil base. Uniquely, each coil support extends away from a first surface of the coil base and maintains one of the coils spaced apart from the first surface of the coil base. With this design, the coil supports allow for direct cooling on both sides of each coil. Additionally, because the coils are spaced apart from the first surface of the coil base, heat transfer to the first surface of the coil base can be minimized.
Preferably, each coil support extends between an inner perimeter of one of the coils and the first surface of coil base. Because each coil is retained by its inner perimeter, each coil is allowed to expand laterally with minimal stress and minimal thermal deformation.
The coil assembly can also include a plurality of spaced apart, individual covers that are secured to the coil base. Each cover encircles a portion of one of the coils and one of the coil supports. Each cover is sized and shaped to provide a fluid passageway between each coil and each cover. Alternately, for example, a single cover can be used to encircle a plurality of coils.
The present invention can also include a fluid source providing a cooling fluid to the fluid passageways to cool the coils. The location of an inlet and an outlet to each fluid passageway can be varied. For example, one or more inlets and/or one or more outlets could extend through the coil base into each fluid passageway.
The present invention is also a method for manufacturing a coil assembly for a linear motor. The method includes providing a plurality of coils, and securing the coils to the coil base with each coil spaced apart from the first surface of the coil base. The method can also include the step of directing a fluid around the sides of each coil to cool each coil.
Additionally, the present invention is directed to a method for making an exposure apparatus that forms an image from a first object onto a second object, and a method for making a device utilizing the exposure apparatus.
Importantly, the coil supports provide a simple and rigid way to individually secure the coils to the coil base. Further, the coil supports thermally isolate the coils from the first surface of the coil base and provide space around both sides of each coil for directing a fluid. With the design, it is easier to maintain external surfaces of the electric motor at a set temperature. Further, the coil supports allow the coils to expand laterally with minimal stress.
REFERENCES:
patent: 3855485 (1974-12-01), Matsui et al.
patent: 4625132 (1986-11-01), Chitayat
patent: 5138206 (1992-08-01), Schmidt
patent: 5777403 (1998-07-01), Yuan
patent: 5783877 (1998-07-01), Chitayat
patent: 6084319 (2000-07-01), Kamata et al.
patent: 6-62786 (1994-09-01), None
Binnard Mike
Hazelton Andrew J.
Jones Judson H.
Nikon Corporation
Ramirez Nestor
Roeder Steven G.
Rose Jim
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